AFIRMATIVE
Example: You like coffee.
Subject+verb(e)s+object.
She likes coffee.
NEGATIVE
3rd person singular.
Subject+does not/doesn't+verb+object.
She doesn't like coffee.
Subject+do not/don't+verb+object.
You don't like coffee.
INTERROGATIVE
Do+subject+verb+object?
Do you like coffee?
3rd person singular.
Does+subject+verb+object?
Does she like coffee?
Rule 1:
In the affirmative of the present simple to all the verbs an -s is added at the end. Do not forget that, when being in negative and interrogative sentences, the -s should not be put.
When verbs end in -o, -sh, -ch, -ss, -x and -z you must add -es to the end.
For verbs ending in -y, you must replace -y with i and the add -es.
There is another exception for verbs ending in -y. When there is a vowel before the -y, you must keep it and add the -s.
Rule 2:
In the third person, does is the auxiliary you should use; however, do is used for the first and second person singular and plural.
Rule 3:
To be is the most used irregular verb in English, so we recommend that you study and learn all its forms of conjugation.
Rule 4:
To use the present simple with the moral verbs (can, must, may), you must be ar in mind that there are two exceptions. You should never add -s or -es to them. When using the present simple in negation and question sentences, modal verbs must never have the do/does auxiliary.
To express habits, general truths, repeated actions or unchanging situations, emotions and wishes:
I smoke (habit); I work in Guayaquil (unchanging situation); Guayaquil is a large city (general truth)
To give instructions or directions:
You walk for five hundred meters, then you turn left.
To express fixed arrangements, present or future:
Your exam starts at 07.00
To express future time, after some conjunctions: after, when, before, as soon as, until:
He'll give it to you when you come next Monday.